An Oklahoma teenager who killed an Australian college baseball player has been sentenced to life in prison without parole.

Chancey Allen Luna, 18, was convicted of first-degree murder by a Stephens County jury in the August 16, 2013, killing of 22-year-old Christopher Lane.

Authorities say Lane was shot in the back while he was jogging in Duncan. Defense attorneys say Luna, who riding in a friend's car, fired the shot, but only meant to scare Lane.

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Chancey Allen Luna (left), 18, was sentenced to life in prison without parole for killing Australian college baseball player Christopher Lane (right), 22, in August 2013

Luna, pictured here after being convicted of first-degree murder in April, apparently showed no emotion at his sentencing

Defense attorneys say Luna was riding in a friend's car when he fired the shot. He had only meant to scare Lane, not hit him, attorneys said

Lane, from Melbourne, Australia, was in Oklahoma on a baseball scholarship. He was a catcher and preparing for his senior year at East Central University in Ada and was visiting his girlfriend and her family in Duncan when he was shot.

'There was no motive, no plan to kill anyone,' defense attorney Jim Berry had said during his opening statements.

District Court judge Ken Graham delivered the sentence recommended by the jury in April after Luna was found guilty. Luna showed no emotion after he was sentenced.

He was also stone-faced when he was convicted in April, only saying 'sorry' to a swarm of reporters as he left the courtroom.

Lane (pictured here with his girlfriend), from Melbourne, Australia, was in Oklahoma on a baseball scholarship as a catcher at East Central University in Ada and was

Lane had been visiting his girlfriend, Sarah Harper (left) and her family in Duncan, Oklahoma when he was shot

Luna was 16 at the time of the 2013 shooting and the court heard he was a member of the infamous Crips street gang.

On the back of his orange prison jumpsuit in court on Tuesday was 'Crips for Life', written in black pen.

'Sixteen is a very, very young age, but we are also talking about an innocent man not much older,' Graham told Luna.

At Luna's April trial in Duncan, Oklahoma, a jury only took an hour to find the teenager guilty of first-degree murder.

Lane's parents and sister, who had read heartbreaking victim impact statements before the verdict was announced, expressed satisfaction with the outcome of the trial.